Baseball plays an important part in Alan Zweibel’s “Happy,” easily the best play in “Summer Shorts 4: Series B,” a collection of one-acts that, as a whole, bats .250.

The piece concerns the meeting between a sports memorabilia dealer, Donald (Scott Adsit, moonlighting from TV’s “30 Rock”), and a janitor, Happy (Arthur French), whose promising career with the Mets was cut short decades ago by an injury.

Donald wants Happy to autograph a baseball signed by his Met teammates — but he’s after more than the $28,000 the ball will fetch on the open market. With equal amounts of humor and sentiment, “Happy” is a treat.

The rest of the lineup is pretentious, baffling or both. Wendy Kesselman’s “The Graduation of Grace” has an eighth-grader delivering a commencement speech before stripping to her underwear, reciting poetry and doing an interpretive dance.

“Fit,” by Neil Koenigsberg, depicts the bizarre roundelay among a personal trainer, his girlfriend and an effete British client. Finally, Christopher Stetson Boal’s “Jonathan Blaze” concerns a tense encounter between two men, one of whom brandishes a gun and threatens to set himself on fire.

Apparently, it has something to do with an incident in Iraq — mainly, it proves that when a play begins with one character holding a gun on another, it doesn’t have anywhere else to go.